This invention relates to seat belt assemblies for use, for example, on motor vehicles for minimizing the harmful results of a traffic accident, and more specifically to a retractor for such seat belt assemblies. Still more specifically, the invention deals with an emergency locking retractor for seat belt assemblies which is of the type having a locking mechanism activated upon extension of the belt, such as webbing or strap, at a high acceleration for immediately restraining the belt from any further extension.